Patients with bulimia nervosa and anorexia nervosa have abnormalities in serotonin-mediated neuroendocrine responses, suggesting that dysregulation of central nervous system (CNS) neurotransmitter pathways may also contribute to abnormalities in eating patterns. This project will test the hypothesis that in individuals predisposed to development of an eating disorder, serotonergic systeems are not able to adapt to situations, such as dieting, in which decreased tryptophan is available for serotonin synthesis.